Hortus Botanicus Leiden, Netherlands

Common name: Japanse walnoot, Sieboldwalnoot, Japanese walnut, Heartnut, Himegurumi

Family: Juglandaceae (Walnut family)

Synonym: Juglans sieboldiana var. cordiformis

Distribution: Japan

Hardiness: Zone 04

Life form: Tree

Comments: This walnut is native to Japan and was introduced to the botanical garden by the German physician and collector Von Siebold in 1859 and planted in the “nut tree field”. In a heavy storm in July 2015, the trunk was split in two and the tree had to be heavily pruned. Nevertheless, it continues to produce new leaves: a real diehard!
The twigs of this tree are dark grey in colour and have stalked glands. The leaves, which can grow up to 60-90 cm in length, are pinnate. The 11-19 leaflets that form this compound leaf are approximately 8-17 cm in length with a downy lower side. The leaf margins are serrated. The male flowers are catkins of about 8 cm long. The female inflorescences form clusters of 10-20 inflorescences. The nuts hang from long stalks and are covered by a hairy husk. They are ovate and pointed, with a thick protruding seam, and very hard. In Japan they are much valued as an edible nut.